Electrically heated fabric



May 9, 1939. A. cA HARRIS 2,157,606

ELEGTRICALLY HEATED FABRIC Filed July 6, 1937 2 Sheets-Sheet l l N E N T C R Alexander @mf/e5 Har/75.

s S M MAMJ ATTO .QN EY May 9, 1939- A. c. HARRIS 2,157,606

ELECTRICALLY HEATED FABRIC Filed July 6, 1957 2 Sheets-Sheet 2 l N V E N T O R /exander U70/'A95 Har/'f5 BY EWSM ATTO N EY Patented 9, 1939 ELECTRICALLY HEA'IIED FABRIC Alexander Charles Harris, Letchworth, England Application'ruly s, 1937, seal No. 152,191 In Great Britain July 8, 1936 17 Claims.

This invention relates to fabrics, pads, carpet underlays, clothing and the like of the kind in which electrical resistance wire is incorporated to be used for warming or heating, the term fabric being used in the following description and appended claims in a generic sense to include both fabric made in the piece and any articles made of fabric to which the invention is capable of application.

'Ihe present invention provides an electrically heated knitted fabric having an electric resistance Wire incorporated during fabrication or production, i. e., by the automatic operation of the machine as a step in its production of the fabric.

It is primarily the intention to carry the invention into effect in the production of blankets, pads and the like and fabric knitted in the piece or in continuous lengths which may be afterwards cut up for manufacture into clothing and other articles, but the invention admits of broader application, that is to articles which are actually produced on knitting machines, weft or warp, flat or circular.

The electric resistance wire may be incorporated in the knitted fabric weftwise, walewise or in the case of warp fabrics warpwise, or in both directions. From this it will be understood that knitted fabric according to the invention may be produced on knitting machines generally, such as straight bar, flat and circular, weft knitting machines and warp knitting machines.

In this specification and the appended claims the expressions now to be set out are used, where the context so admits, with the following meanings:

Warp knitted fabric means warp fabric incorporating warp stitches or loops produced by simple chain lapping as well as other classes of warp knitted fabric, e. g. close warp fabric and open warp fabric, plainand fancy, made according to any of the well known principles of warp knitting.

"Weit cord means an electric resistance wire, bare or insulated, and/or a wire carrying cord (such, for example, as the wire-carrying cord indicated at 2 in Figure 2 of the accompanying drawings) wherein a. resistance wire is coiled around a core or otherwise made a part of suc cord. 1

Carried weft cord means a weft cord whichis carried, i. e., held, embraced or surrounded, or encircled, by knitted loops of the fabric, including one-ply fabric, and is not, either itself alone or in association with any other yarn, thread or similar structural element `oi the fabric, knitted into loops.

Straight carried weft cord means a weft cord which is laid in straight traverses or courses to and fro across the width of a fabric, or, in circular knitting, around a tube of fabric, and which is carried, i. e., held, embraced, or surrounded or encircled, by knitted loops of the fabric, including one-ply fabric and is not, either itself alone or in association with any other structural element of the fabric, knitted into loops.

Interlooped cord means a wire and/or a wirecarrying cord such as above mentioned which either itself or themselves alone or in association with other structural elements of a fabric is or are knitted into loops.

Of the various types of knitting available for carrying out the invention it is preferred to ernploy warp knitting, in which instance straight carried weft cord is preferably held, embraced or surrounded by (i. e., carried in or encircled by) knitted loops or stitches of the Warp knitted yarn or warp chains of the fabric, including one-ply fabric, throughout its traverse to and fro across the fabric either in each immediately successive row of loops or in each predetermined 'row of loops which in sequence of knitting follows upon a predetermined number of rows of empty loops or parallel Warp chains made by simple chain lapping.

'I'he reason for this preference is that a Warp knitted fabric incorporating straight carried weft cord gives all of the following advantages whilst no type of interlooped cord knitting can give all of them:

(a) No part of the straight carried weft-cord is brought into contact or close proximity with any other part of said cord;

(b) The cord is not coiled upon itself nor is it so bent and looped as an element in loops of other yarns that parts of it adjoin or Contact with other parts;

(c)4 Each traverse of the weft cord is separated from every other traverse by the thickness of the yarns of two loops and may be` separated further by any number of rows of empty loops of the warp chains;

(d) Each traverse of the weft cord, except for the distance occupied on the selvedge for the movement from the end of one traverse to the beginning of another, lies between the front and back of the fabric and is thus substantially enveloped by it so that the weft cord is but little, if at all, exposed at the front or back of the fabric and is thereby protected by the knitted loops. y

(e) When the traverses are separated as just mentioned this permits of any predetermined length and section of weft cord being distributed evenly through fabric.

(j) A fabric can be produced with two adequate selvedge edges.

(g) A fabric of considerable length can be produced incorporating a continuous and great length of resistance wire with no or very few, joinings of the wire;

(h) The distribution of electric resistance wire over any required area of fabric can be effected with a minimum number of bends in the carried weft cord.

(i) There can be employed, carried in the loops of simple warp chains, and without affecting determination of the thickness pr counts of the knitted or interlooped yarns, a wire or wirecarrying cord (within limits) any thickness and measure of flexibility thus freeing determination of the thickness or counts of all the knitted yarns from all other considerations than those affecting ease of knitting and quality of the product, and making possible maximum ease and speed of knitting and production of a very light and flexible fabric.

The advantages (a) to (d) permit of the use of a bare wire or a wire with only a light insulating wrapping.

In order that the invention may be more clearly understood and readily carried into effect, a practical example thereof as applied to a knitted blanket or the like will now be described With reference to the accompanying drawings, wherein,

Figure 1 is a general perspective view of the article shown in a partly folded condition for the sake of convenience in illustration.

Figure 2 is a diagrammatic representation of a portion of the fabric of which the said article is made.

Figure 3 represents a portion of the blanket at one corner thereof and shows the manner in which the electrical resistance wire is connected to a lead.

Figure 4 is a detail View of a portionof the front of the fabric shown in Figure 2.

Like parts are designated by similar reference characters throughout the drawings.

According to the example of the invention illustrated in the drawings, there is provided a blanket I or the like (see Figure 1) made of warp knitted fabric in which a weft cord 2 is straight carried. In a particularly simple and practical form shown in Figure 2 the fabric consists simply of independent Warp chains 3, such as chains of warp knitted or crocheted loops or stitches formed by simple chain lapping with the straight carried weft cord 2 which includes an electrical resistance wire 4 incorporated in successive traverses or horizontal rows oi' loops or stitches from side to side of the fabric so that the weft cord is held by the said loops or stitches whereby not only are the warp chains held together but the traverses of the said cord are also held in parallel relation. Such a knitted fabric may be readily produced on a warp knitting machine adapted for the production of fabric composed of weft threads and enchained warp threads, a machine of this character being for that purpose fitted with a weft cord carrier or carriers in addition to the usual warp guider. With a machine of this particular type the weft cord or cords is or are laid rapidly and in such a way that no strain is imposed thereon. Other machines may, however, be employed or adapted to produce similar results.

, Instead of being incorporated in the fabric as astraight carried weft cord or an element in such a cord, the wire. may be incorporated in the fabric as an interlooped cord alone or in conjunction with a straight carried cord ln any customary manner of knitting carried out on a straight bar, fiat or circular machine, or upon awarp knitting machine.

According to the present invention, it is desirable that fine electric resistance wire be used in electric knitted fabric.

As against the use of such wire in its naturally drawn or extruded form it is preferred to use it wound or coiled upon a core in such a manner as to reduce greatly, if not eliminate entirely, the possibility of breaking or kinking, this being especially applicable if the Wire is to assume a looped condition as the result of its incorporation in the knitted fabric. The aim here is to simplify knitting so that it can be done by sultable machinery for producing electrically heated fabric cheaply.

In the specific example illustrated, the electric resistance wire 4 is wound spirally on a core 5 of suitable material adapted during the knitting process and afterwards, when incorporated in the knitted fabric, to take all or most of the strain to which the wire would otherwise be subjected. The fact of winding the wire on a core enables a great length of low resistance wire to be incorporated in a comparatively small area of the fabric rather than employ a lesser length of higher resistance wire in the same area.

'I'he core may consist of one or more threads, yarns, cords, or lengths 6 of wool, cotton insulating or other material suitable for the intended purpose. 'I'he core should however be flexible, capable of assuming a looped formation when necessary and of withstanding the strains incidental to the knitting process and the use to which the fabric is to be put. As will be understood, the wire is wound spirally upon the core preparatory to being incorporated in the knitted fabric; the core thus serves ,as a carrier for the wire.

In most cases it is preferable to use a core or carrier material which is incapable of stretching to more than a negligible extent, as for example a textile yarn of wool or cotton or a mixture of these, although a core or carrier material of an elasticity permitting greater stretch may be used but the stretch preferably should not be in excess of a degree likely to prevent the core or carrier relieving the coiled wire of such strain as is likely to cause breakage.

The textile yarn forming the basis of the knitted fabric may serve to insulate or' prevent contact of adjacent strands of the weit cord, in which case the electrical resistance wire used may be bare. 'I'he wire may, however, be covered with a suitable insulating material, especially when incorporated both warpwise or weftwise, or when wefts and/or warps are incorporated in close proximity to each other. In the example illustrated, see more particularly Figure 2, the electrical resistance wire 4 is covered las at 1 with an insulating enamel, the enamel is covered with silk or similar material 8 and, after being wound on the core 5, the coil of wire is finally wrapped with a suitable insulatlng textile yarn 9, such as wool or cotton or a mixture of these. Thus, since the wire (when used as an element of a straight carried weft cord) is finally embedded in the centre of the knitted fabric, there are provided four separate insulations which make the fabric particularly safe as regards avoiding the possibility of users receiving electric shocks. Instead of, or in addition to, providing the silk or similar covering 8, the wire 4 may be waterproofed with an insulating varnish which is substantially reproof. In

/this instance the varnish, which would not be detectable on the outside of the covering 9, would serve also to cause the said covering to adhere to the core 5.

If desirgi, one or more wires may be spirally wound round the same core.

The weft cord may be incorporated throughout the length or in a part or parts only of the knitted fabric. It is an advantage to incorpor'ate it weftwise as it will be continuous throughout the fabric or the part or parts in which it is located. If incorporated as warps the separate warps require to be joined or connected at the ends.

In a length of fabric produced on a flat or straight bar knitting machine the incorporated weft cord is exposed somewhat at each selvedge. Accordingly, as shown in Figure 1, the outer edges of the Wired part Ill are bound with lengths of tape II which are suitably folded and secured to the fabric, for example by suitable rows of stitching such as I2 and I3. The rows of stitching I2 extend parallel to the wefts 2. When stitching tape to the ends of the article I care must be taken to ensure that the stitches of the rows I3 are inserted between the Wefts as shown in Figure 3. The article is conveniently adapted to be connected to any suitable source, of current supply by means of a flexible lead I4 having at one end thereof an electrical connecting plug I5. At its other end the lead is conveniently secured, by means of a length I6 of any suitable binding material, within a tubular extension II formed of the tape at one corner of the blanket. 'I'hus the twin wires I8 and I9 of the lead project into a pocket formed between the folded tape. In Figure 3 part of the tape is represented as being torn away to show the electrical connections more clearly. The wire I8, together with its customary insulating covering, is bent into the form of a loop 2| to prevent undue strain on the wire. The latter is joined to one of the free ends of the coiled electrical resistance wire 4 and the loop 2l, together with the free end of the weft l2 at the side of the article, are bound by insulating tape or the equivalent, 22. If desired, the end of the wire 4 just referred t'o may be clamped or joined to the wire I8 by means of a small tag, or by a small strip of metal. Similarly the wire I9 together with its insulating covering is bent into the form of a loop 23. The said wire is joined to the opposite end of the resistance Wire Y4 and a strip of insulating tape or the equivalent 24 is employed to complete the connection. Here again, and if desired, the appropriate end of the wire 4 may be clamped or joined to the wire I9 by a small tag, or by a strip of metal. In the specic example illustrated, the end of the coiled resistance Wire 4 at the side of the article remote from the electrical connections extends through the tape binding at' the appropriate end of the article so that it can readily be joined to the wire I9. Preferably, and as shown more clearly in Figure 3, the tape at this end of the article is stitched as at 25 to form a tunnel 26 through which the portion or return lead 21 of the coiled resistance wire can pass.

In a fabric produced on a warp knitting machine of the type hereinbefore referred to the weft cord may be incorporated together with a textile weft of cotton, wool or other suitable yarn.

'I'here may be provided in association with the fabric a thermal cut-out or fuse of any suitable conventional form to protect the fabric against excessive rise of temperature when used ir/Lconflned spaces.

Alternatively, or in addition, I may combine with my improved fabric one or more thermostats or any suitable conventional form for the purpose of compensating for any undue retardation of the normal rate of escape of heat from the fabric due, for example, to, leaving piled over a blanket an undue quantity of bed clothing, or leaving a hassock upon a carpet u-nderlay. When provided, the thermostat or each thermostat is provided in association with the resistance wire, wrapped in any suitable material and disposed on the exterior of the fabric or article.

In association with my electric textile fabric I may use fuses in the electrical connections, for instance in the electrical connecting plug, to protect the flexible connection to the fabric, as well as the latter.

The cross-section, length and material of the coiled resistance Wire incorporated in my electric textile fabric are such as to provide in a finished article a heating surface giving maximum effect, that is t'o. say, are such as will enable a given quantity of electrical energy to heat the surroundings of the article to the required extent with a minimum rise of temperature in the resistance wire itself.

The blanket illustrated in the drawings is capable of being used in many ways. It may, for instance, be used as a bed warmer, as a rug to throw over the knees and as a means of drying and airing household linen.

Various modifications may be made in this invention without departing from the spirit thereof or the scope of the claims, and therefore the exact forms shown are to be taken as illustrative only and not in a limiting sense, and it is desired that only such limitations shall'be placed thereon as are disclosed in the prior art or are set forth in the accompanyingv claims.

What I claim as my invention is:

l. A'n electrically heated knitted fabric having an electrical resistance Wire incorporated therein, said resistance wire being incorporated by the automatic operation of the knitting machine during fabrication of the fabric Without being formed into knitted loops.y

2. An electrically heated knitted fabric in which electrical resistance wire isincorporated lhaving a carried weft cord.

3. An electrically heated knitted fabric in which electrical resistance wire is incorporated having a straight carried weft cord.

4. An electrically heated knitted fabric in which electrical resistance wire is incorporated having a carried weft cord and an interlooped cord.

5. An electrically heated fabric in which the basic textile yarn is warp knitted, including a weft cord held by at least some of the loops of the warp knitted yarn.

6. An electrically heated fabric in which the basic textile yarn is warp knitted and includes warp chains made by simple chain lapping and a weft cord incorporated in the fabric, said cord being held by at least some of the loops of the warp chains.

7. Electrically heated knitted fabric comprising warp chains formed by simple chain lapping knitted side by side in parallel and a straight carried weft cord traversed to and fro across the chains and throughout each traverse from side to side of the fabric, said weft cord being held in the loops of each succeeding row of loops of the chain.

8. An electric heating body comprising a knitted fabric having an electrical weft cord incorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being carried solely by the knitted loops of the fabricwithout forming part of said loops.

9. An electric heating body comprising a knitted fabric having an electrical weft cord incorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being carried solely by the knitted loops of the fabric without being formed into loops.

10. An electric heating body comprising a knitted fabric having an electrical weft cord therein, said cord being carried solely by the knitted loops of thel fabric without forming part of said loops and without being formed into loops.

11. An electric heating body comprising a knitted fabric having an electrical weft cord incorporated by the automatic operation of the knitting machine during the fabrication of the fabric, said cord being carried solely by the knitted loops of the fabric and forming an indispensable part of the fabric without forming part of said loops.

12. An electrical heating body comprising a knitted fabric having an electrical weft cord incorporated by the automatic operation of the knitting machine during the fabrication of the fabric, said cord being carried solely by the knitted loops of the fabric, and holding said loops together without being formed into loops.

13. An electrical heating body comprising a knitted fabric, said fabric being warp knitted and having an electrical weft cord incorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being carried solely by the knitted loops of the fabric without forming part of the said loops.

14. An electrical heating body comprising a knitted fabric, said fabric being warp knitted and having an electricalv weft cord incorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being carried solely by the knitted loops of the fabric and holding said loops together without being formed into loops.

15. An electric heating body comprising a knitted fabric, said fabric being warp knitted and having an electrical weft cord therein, said cord being carried solely by the knitted loops of the fabric and forming an indispensable part of the fabric without forming part of the loops and without being formed into loops.

16. An electric heating body comprising a knitted fabric, said fabric consisting of warp chains knitted side by side in parallel and having an electrical weft cordincorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being laid in traverses toand fro across the chains from side to side of the fabric, and said cord being carried by each immediately succeeding row of loops of the chains without forming part of the loops to form an indispensable part of the fabric.

17. An electric heating body comprising a knitted fabric, said fabric consisting of warp chains knitted side by side in parallel and having anelectrical weft cord incorporated by the automatic operation of the knitting machine during fabrication of the fabric, said cord being laid in traverses to and fro across the chains from side to side of the fabric, and said cord being carried by each predetermined row of loops of the chain which follows on sequence of knitting upon a. predetermined number of empty loops of the chain without being formed into loops to hold the chains together.

ALEXANDER CHARLES HARRIS. 

